PHILIP A. MUNZ 5 



that the vein A at the base of the wing is fused with Cu, but crosses 

 the space back of Cu and then proceeds as formerly thought 

 toward MA. He therefore proposes the name "anal-crossing" 

 (Ac) for this apparent cross-vein, and the abbreviations Ab for the 

 bridge toward the wing-base, and A' for the distal portion of the 

 anal vein. This system will be used in this paper when especial 

 attention is called to some part of this vein, otherwise A alone will 

 be used to designate the anal vein in general; the sign 1st A is not 

 necessary since the Zygoptera possess only one anal vein. I agree 

 with Mr, Tillyard that the sign A followed by an asterisk as used 

 by Dr. Ris is unfortunate; when I read one of his descriptions I find 

 myself involuntarily looking to the bottom of the page for the foot- 

 note which I always associate with the use of the asterisk. 



Mr. Tillyard's contention (1915) and that of Dr. Ris (1916a) 

 that the Zygoptera present a difTerent condition than that of the 

 Anisoptera in the branching of the radius do not seem well founded. 

 To be sure none of the nymphs of the Zygoptera that have yet been 

 examined show the trachea Rg crossing over that of M1+2 as do the 

 Anisoptera, however it seems inconceivable that the vein Rg of the 

 Anisoptera can have in the Zygoptera a vein so completely analo- 

 gous in position and yet not be homologous. Mr. Tillyard's 

 name "median sector" is a matter of words only; it indicates 

 no homology to the veins of any other order, although in retaining 

 the same name for the different branches of media he admits that 

 the media has exactly the same position in both suborders, which 

 state cannot be true if the radius does not present the same con- 

 dition in both. Professor Needham (191 7) has shown how many 

 of 'Sir. Tillyard's arguments can be used to support the opposite 

 view of the case. I therefore have no hesitation in following the 

 usual system of nomenclature. 



As an example of the Agrionidae the genus Agrion {Calopteryx) 

 may be used with the abbreviations given in fig. A. These abbre- 

 viations are given as follows: 



C=costa, Sc=subcosta; Ri = radius-one, R,,= radical sector; 

 Mi = media-one, M2 =media-two, M3 = media-three, M4=media- 

 four, Mia = the longest sector between Mi and M2; Cu = cubitus, 

 Cui = cubitus-one, Cuo =cubitus-two, Cu2a=a branch of Cu2 



MEM. AM. ENT. SOC, 3. 



